Former Columbia University researcher Sambuddho Chakravarty has found that although Tor was designed to enable users to anonymously browse the Internet, 81 percent of those using Tor can be de-anonymized by exploiting a technology in Cisco routers called Netflow that can reveal a user’s originating IP address. The Netflow exploit is the latest in a series of incidents indicating Tor is not a foolproof security system. “Tor runs on top of a complex series of interconnections between apps and the underlying network,” says SecureIdeas CEO Kevin Johnson. “To expect that everything in that system is going to understand and respect it, it becomes very complex.” Netflow breaks down Internet traffic into its various types, for example 50 percent email, 35 percent Web traffic, and the remainder being Tor. Chakravarty’s method for exploiting Netflow works by injecting a repeating traffic pattern into the connection and then checking the router’s flow records to find a match. If the system finds a match, then the user is no longer anonymous. Chakravarty is now researching network anonymity and privacy at the Indraprastha Institute of Information Technology in Delhi.